Thread severing mechanism



July 13, 1965 .1. CHUDNER THREAD SEVERING MECHANISM 5 Sheets-Sheet 1 Filed Dec. 27, 1 62 INVENTOR.

JQSEPH CHQDNER ATTOR/Vf y 1965 J. CHUDNER 3,194,198

THREAD SEVERING MECHANISM T llllll INVENTOR.

QOsEPH C HUDNER ATTOIP/Vf)" July 13, 1965 CHUDNER 3,194,198

THREAD SEVERING MECHANISM Filed Dec. 27, 1962 5 Sheets-Sheet 3 INVENTOR. JOSEPH CHUDHER ATTORNEY y 1965 J. CHUDNER 3,194,198

THREAD SEVERING MECHANISM Filed Dec. 27, 1962 5 Sheets-Sheet 4 INVENTOR.

JOSEVH CHUDN ER ATTORNEY July 13, 1965 J. CHUDNER 3,194,198

THREAD SEVERING MECHANISM Filed Dec. 27, 1962 5 Sheets-Sheet 5 i U l'/5 L s I: 12352 F/G. l5

INVENTOR. QosEPH CH owl E ATTORNEY United States Patent Filed Dec. 27, 1962, Ser. No. 247,625 18 Claims. (Cl. 112-252) This invention relates to thread severing mechanisms for sewing machines, and more particularly relates to a mechanism for cutting both the needle thread and the bobbin thread at points very close to the outer surface of the material being stitched so that subsequent trimming of such threads is not required.

In commercial operations utilizing sewing machines for the mass production of stitched articles, such as in the garment trade, the sale price of the stitched article produced is necessarily related to the labor cost involved in producing the same. Accordingly, reductions in the fabrication time of a stitched article result in the ability to sell such articles at a lower price, and labor saving devices are therefore of great interest to the trade. During the stitching process, it is frequently necessary to sever the needle and bobbin threads while the fabric being stitched is centrally located relative to the needle, that is, when the line of stitching does not terminate at or near the edge of the fabric. Generally, in such a case, the work must be displaced from its position at the end of the line of stitching so that sui'ficient of the needle and bobbin threads become available for hand cutting, the work being then repositioned in the proper place for starting the next line of stitching. After the stitching operations have all been completed it is then necessary to trim off all the projecting thread ends so that the stitched article may present a neat and finished appearance. Such a thread cutting operation is time consuming and can contribute materially to labor costs associated with the production of a particular stitched article.

In order to alleviate this thread trimming problem, attempts have been made in the past to provide automatic thread cutting means designed to leave a minimum of thread to be trimmed and which in some cases could be ignored. One such thread cutting means has been mounted to the rear of the presser foot to cut the thread by a vertical down stroke of a cutting edge. This type of apparatus, of course, could only be used at the edge of a fabric where the fabric is shifted out from under the needle and behind the vertical cutting device, in order that the cutting stroke should cut only the thread and not the underlying fabric as well. The vertical cutting devices are therefore of limited use, being helpful only in those cases where the line of stitching terminates at the edge of the stitched article.

Other mechanical cutting arrangements have been devised which cut the thread by a cutting stroke in a plane parallel to the surface of the fabric being stitched. Such devices can of course be utilized when the fabric is centrally located under the needle without requiring that the fabric be removed from the sewing machine. However, even cutters of this type generally leave thread ends of approximately /a of an inch and the need for subsequent trimming of the short ends remains. My invention on the other hand provides for cutting of the needle and bobbin threads within a few hundredths of an inch of the fabric Surfaces and consequently eliminates the need for subsequent trimming.

Brieflly, my invention accomplishes thread cutting by apparatus including a pair of hot wires which rapidly burn through the threads to be severed. One of these wires is associated with the presser foot and serves to sever the needle thread, while the other wire is associated with the throat plate above the bobbin and serves to sever the bobbin thread. These hot wires are only energized when so desired by the sewing machine operator, so that during a normal stitching operation there is no tendency whatever for needle thread and bobbin thread to be prematurely severed. Additionally, means are also provided for insuring that the sewing machine may be again immediately utilized after a thread cutting operation without having to re-thread the needle. Accordingly, it is a primary object of my invention to provide a novel thread cutting apparatus effective when actuated to sever the needle thread and bobbin thread of a sewing machine very close to the outer surfaces of an article being stitched to thereby eliminate the need for subsequent hand trimming of short thread ends.

Another object of my invention is to provide a novel thread cutting apparatus for severing the needle thread and bobbin thread of a sewing machine close to the surfaces of a stitched article by means of operator controlled and selectively energizable hot wires.

Yet another object of my invention is to provide novel thread cutting apparatus which permits the needle thread and bobbin thread associated with the sewing machine to be cut without displacing the article being stitched from the position it occupies at the end of the stitching operation.

A further object of my invention is to provide novel thread cutting apparatus including means for insuring that the thread cutting operation does not unthread the needle of the sewing machine.

The foregoing and other objects of my invention will become clear from a reading of the following specification in conjunction with an examination of the appended drawings, wherein:

FIGURE 1 is a fragmentary elevational View showing the working end of a sewing machine head as seen looking into the front of the presser foot, illustrating one view of the thread cutting system and the auxiliary means employed to provide thread tension release in order to avoid re-threading of the needle after the thread cutting operation;

FIGURE 2 is an endelevational view of the sewing machine head illustrated in FIGURE 1 illustrating certain organizational details of the bobbin thread severing mechanism not visible in FIGURE 1;

FIGURE 3 is a rear elevational view of that par-t of the sewing machine head which 1s seen in FIGURE 1 illus trating certain details of the mechanical arrangement utilized to clamp the needle thread and prevent unthreading of the needle;

FIGURE 4 is a view of the apparatus according to the invention as would be seen when viewed along the line t-4 of FIGURE 1;

FIGURE 5 is a perspective view of the apparatus for clamping and severing the needle thread and releasing the tension thereon, illustrated as removed from its mounted position on the sewing machine head;

FIGURE 6 is a perspective view of the bobbin thread severing mechanism seen in elevation in FIGURE 2 but demounted from the sewing machine structure;

FIGURE 7 is a rear perspective view of the needle severing mechanism seen in front perspective in FIG- URE 5;

FIGURE 8 is a rear perspective of the bobbin thread severing mechanism shown in front perspective in FIG- URE 6;

FIGURE 9 is an enlarged plan view of the presser foot illustrating the needle thread clamp in closed position as during a normal stitching operation;

FIGURE 10 is similar to the showing of FIGURE 9 excepting that the needle thread clamping mechanism is 35 illustrated in open condition just prior to clamping the needle thread and severing the same;

FIGURE 11 is an enlarged fragmentary showing of the forward end of the presser foot shown in FIGURE with the thread clamping plate over the righthand presser foot toe partially removed to disclose the underlying hot wire structure;

FIGURE 12 is a vertical sectional view taken through the center of the presser foot structure as would be seen when viewed along the line 12-42 of FIGURE 9;

FIGURE 13 is a vertical sectional view taken through the toes of the presser foot and at right angles to the showing of FIGURE 12 as would be seen when viewed along the line 13-I3 of FIGURE 12;

FIGURE 14 is a vertical sectional view through the throat plate of the sewing machine as would be seen when viewed along the line I4I4l of FIGURE 6 showing certain details of the bobbin thread severing mechanism;

FIGURE 15 is a vertical sectional view taken through the throat plate of the sewing machine and disclosing certain details of the bobbin thread cutter portion of the apparatus as would be seen when viewed along the line I5-15 of FIGURE 14;

FIGURE 16 is an underside plan View of the throat plate of the sewing machine modified in accordance with the invention to carry the hot wire thread cutting mechanism for severing the bobbin thread;

FIGURE 17 is similar to FIGURE 16 excepting that a portion of a slider device has been sectioned away to disclose the underlying hot wire structure; and

FIGURE 18 illustrates in enlarged perspective the throat plate slider device and its organization with the hot wire bobbin thread severer.

In the several figures, like elements are denoted by like reference characters.

Turning to an examination of the figures, there is seen in FIGURES l to 4 a sewing machine head designated generally as 2% provided with a plurality of thread guides 21 through 26, thread tensioner 2'7, thread take-up lever 28, needle bar 29 carrying needle 3f through which is threaded in usual fashion a thread 31. Disposed behind the needle bar 29 is the presser foot bar 32 carrying presser foot 33 shown in operative position seated downward upon the feed dogs projecting upward through the throat plate 34 of the sewing machine. The throat plate 34 is clip engaged to the sewing machine bed plate 35 below which is operatively mounted in the usual manner the bobbin 3 6. The presence of all of the foregoing described elements in a sewing machine is conventional, but the specific structures of the presser foot 33 and throat plate 34 are not conventional and incorporate respectively the hot wire thread cutting means for severing the needle thread and the bobbin thread. Before describing the additional mechanisms associated with the presser foot and throat plate for energizing and actuating the thread cutting devices per se, it will be conducive to a more complete understanding of the invention to first examine the structure of and mode of operation of the presser foot and throat plate. Considering first the presser foot 33, examine now also FIGURES 5, 7, and 9 through 13.

As best-seen in FIGURES 5, 7 and 12 the presser foot 33 includes a main block 37 fixedly securable to the shiftable presser foot bar 32, an underlying sole piece 38 pivotally secured to the main block 37 by means of pivot pin 39 for pivotal motion in a vertical plane, a vertically extending elongated member 40 disposed fiatwise against the rear face of the presser foot main block 57 and secured thereto for lateral pivotal motion by machine screw 41 projected approximately centrally therethrough and into threaded engagement with the presser foot main block 37, and a thread clamp lever arm 42 pivotally secured for horizontal swinging movement to the upper face of the sole piece 38 by means of machine screw projected downward therethrough into threaded engagement with the sole piece.

Projecting forward from the front end of the sole piece are a pair of presser foot toes and 45 separated by a channel within which the sewing machine needle 3% reciprocates during a stitching operation. As best seen in FIGURES 11, 12 and 13, the presser foot toe 45 is downwardly recessed as at 45 immediately forward of the main portion of the sole piece 38 excepting for the ridge 47 which defines a pair of front to rear spaced channels within which are secured, as by means of an adhesive, a pair of high temperature ceramic insulating sleeves 43. A U-shaped resistance wire element 49 is disposed with its opposite ends within the sleeves 48 and with its base portion disposed substantially horizontally within the recess region 36 and projecting toward but not into the slot between the presser foot toes 44 and 45, these aspects being best seen in the showings of FIGURES 11 and 13. The opposite ends of the resistance wire 49 disposed within the sleeves 43 are electrically connected to a pair of low resistance electrically conductive leads 5t) which extend laterally of the presser foot toe 45 and rearward to points of electrical connection with the plug prongs SI carried by the presser foot main block 37.

Overlying the presser foot too 45 and extending rearwardly therealong above the resistance wire element 49 is a spring plate 52 secured in position by means of the screw 53 and pin 54. Thel-eft edge of the spring plate 52 is recessed inward as at 55 substantially centrally of the resistance wire element 49 to help position the needle thread for severing as will be subsequently seen. Clamping of the needle thread just prior to severance thereof is effected by cooperation between the spring plate 52 and a shiftable thread clamp 56 secured by means of the pins 57 to the thread clamp lever arm 22, the thread clamp 5:: being transversely shiftable relative to the pr-esser foot toes between the two conditions best seen in FIGURES 9 and 10.

As best seen in FIGURES 10 and 11, the thread clamp es is provided at its righthand end with a Vshaped notch 58 which shifts transversely across the slot between the presser foot toes to catch the needle thread and carry it laterally toward the toe 45 and under the spring plate 52 beyond the recess 55. This clamping action is best seen in FIGURE 13 where the thread 31 is seen to be so clamped. As also seen in FIGURE 13, the needle thread III is laid over against the resistance wire 49 so that it would be severed in the event that the resistance wire were heated to a sufficiently high temperature. It will also be noted from FIGURES 9 and 13 thatclamping of the needle thread 31 between the spring plate 52 and thread clamp 56 is effected just prior to engagement of the needle thread 31 with the resistance wire 49 so that burn through of the needle thread cannot occur prior to effective clamping of the thread above the point of severance. Thus, even should the resistance wire 49 be energized prior to engagement of the needle thread 31 therewith it will be appreciated that severance of the thread 31 occurs subsequent to thread clamping.

Also shown on the thread clamp 56 is a front notch 59 of generally V-shape so positioned that the root of the notch is substantially centered between the presser foot toes when the thread clamp 56 is in closed position as shown in FIGURE 9. This front notch 59 permits the sewing machine needle 30 to pass downward in front of the thread clamp 5'6 without physically engaging the latter, this condition being required since the end of the needle thread must be maintained clamped until at least the first subsequent stitch has been taken by the sewing machine.

Opening and closing of the thread clamp 56 is effected by means of an electrically energizable rotary solenoid 6f) operating through a linkage system including the lever member as and thread clamp lever arm 42 carried by the presser foot. The end of the thread clamp lever arm 4-2 is projected freely into a slot 61 cut through the elongated lever member at proximate the lower end thereof, the

upper end of the lever member 66 being terminated in a rearwardly facing stud 62 adapted for disposition within the forked terminating slot at the lower end of lever 63.

Opening of the said clamp 56 occurs when the upper end of the lever member 4-0 is shifted counterclockwise as viewed in FIGURE 5 from the front, or clockwise as is viewed from the rear in FIGURE 7, and closing of the clamp 56 is effected by reverse motion of the lever member 40. These motions are transmitted to the lever member 40 from the rotary solenoid 60 by means of the intervening linkage system including the interconnected lever and link elements 63, 64 and 65, the latter being pivotally mounted upon the rotary drive shaft 66 of the solenoid 60 as best seen in the showing of FIGURE 7. The levers 63, 65 and link 64 are pivotally connected as at 67 and 63 and the lever 63 is pivotally secured to the supporting frame structure designated generally as 70, as by means of the pivot 69. The rotary solenoid 66 is fixedly secured to another portion of the frame structure 70 by means of the bushings 71, one of which extends through a .slot cut through the lever 65. A spring 72 is stretched between an anchor 73 secured to the frame structure 76 and an anchor 74 mounted to the lever 63 below the pivot 69. The lower end of lever 63 is vertically slotted as at 75 and the stud 62 of the presser foot member 46 is disposed therewithin so that the biasing action of spring 72 causes the presser foot lever member 40 to normally maintain thread clamp 56 in a closed position as seen in the showing of FIGURE 9.

Actuation of the solenoid 66 causes lever 65 to rotate counterclockwise as viewed in the showing of FIGURE 7 and to thereby pivot lever63 about the pivot 69 and against the biasing force of spring 72 to open the thread clamp 56 to the position illustrated in FIGURES and 11. Deactuation of the solenoid of course permits the spring 72 to restore the thread clamp 56 to its closed position. Actuation and deactuation of the rotary solenoid 60 is effected by electrical energization and de-energization of the solenoid via electrical conductors 76 connected to the electrical plug prongs 77 carried by insulating block 78. As best seen in FIGURES 3, 4 and 7, a second set of plug prongs 79 are also mounted to the insulating block 78 and a jumper cable (not shown) is employed to connect the prongs 79 to the prongs 51 carried by the presser foot main block 37. If it is desired to energize the presser foot resistance wire 49 simultaneously with the energization of the solenoid 66, and if both are designed to operate from the same voltage, then the prongs 78 and 79 may be strapped together. Alternatively, if it is desired to energize the presser foot resistance wire 49 and the rotary solenoid 60 at different times or with different voltages then the prongs 78 and 79 would not be interconnected but would each be separately energized from a supply cable with the appropriate voltages or at the desired times.

From the showing of FIGURE 13 it will be appreciated that the clamping action of the thread clamp 56 of the presser foot 33 required that a length of thread 31 be drawn from the thread supply through the thread tensioner 27 or else the thread 31 will snap since it cannot elongate sufficiently by stretching. Additionally the shape of the thread clamp 56 makes it clear that the opening stroke thereof causes engagement between the forward edge of the thread clamp and the needle thread with the attendant possibility of thread snapping again being present. The possibility of thread breakage due to the actuation of the thread clamp 56 is prevented by means of a thread tension release mechanism which operates simultaneously with the thread clamp 56 through a cam and lever system coupled tolever 65 actuated by the rotary solenoid 60.

As best seen in FIGURES 3 and 7, a cam 86 provided with a V-slot 81 is pivotally mounted upon rotary solenoid drive shaft 66 and adjustably fixedly secured to lever 65 by means of the locking screw 82 projected through arcuate slot 83 in lever 65 and threadedly engaged with the cam 86. Projecting into cam V-slot 81 is a cam follower stud 34- fixedly secured to the upper end of a crank arm 85 which has its lower end fixedly secured to a transversley extending crank shaft 86 by means of a lock screw 87, the crank shaft 86 extending forward to the front of the sewing machine head through the arms of a U-shaped bearing block 88 as best seen in the showing of FIG- URE 5. The forward end of crank shaft 86 terminates in a bushing 69 having a slotted front face keyway within which is disposed the arm 90 of the needle thread tension release member 91 which terminates at its forward end in an upturned hook 92, the tension release member 91 being locked to the bushing 89 and crank shaft 86 by means of the end screw 93. As best seen in FIGURE 1, the upturned hook 92 of the tension release member 91 is so positioned as to normally not interfere with the operation of the thread tensioner 27, but it will be appreciated that when the hook 92 swings upward between the plates of the thread tensioner it causes the latter to move away from one another and to thereby release the tension upon the needle thread 31.

The motions of the tension release hook 92 are coordinated with the motions of the thread clamp 56 by means of the aforedescribed cam 80 acting upon the crank arm cam follower stud 84- through the cam slot 81. The V-slot 81 of the cam 30 causes the cam follower stud S4 to first rotate the crank arm 85 to cause the tension release hook 92 to release tension of the needle thread 31 during the first portion of the opening movement of thread clamp 56 and to then counter-rotate the crank arm 85 to re-apply the thread tension after the thread clamp 56 is fully open. As the thread clamp 56 begins its closing motion the tension release hook 92 again moves upward for engagement with the thread tensioner 27 to cause tension release by the time the thread clamp notch 58 engages the needle thread 31 and thereafter maintains the tension released until the needle thread has been carried under the spring clamp 52 and effectively clamped, whereupon the tension release hook 92 again is rotated downward to its normal disengaged position from the thread tensioner 27 to allow normal tension to be applied thereto. seen in FIGURE 7, the total throw of the cam follower stud 84 during a complete cycle of operation of the thread clamp 56 is less than that which is permitted by the V-slot 81 in cam 80. This provides the means for adjusting the movements of the tension release hook 92 with respect to the thread clamp 56, such adjustment being efiected by loosening of locking screw 82 and rotating the cam 86 relative to the lever 65 to establish the desired terminal points of the cam follower stud 84 within the V-slot 81.

The frame 70 to which all of the previously described operative parts of the needle thread cutting mechanism are secured is disposed upon the sewing machine head 20 as best seen in the showings of FIGURES 1 to 5 and 7 so that the frame top plate 94 overlies the sewing machine head with the stud 98 disposed within the slot 95 to thereby lock the frame 70 with the plate 96 and machine screws 97. Projecting transversely from rear to fore end of the frame immediately beneath the top plate 94 and above the -shaped bearing block 88 is the bar 99. Secured to the front end of the bar 99 and hearing block 83 by means of the socket head bolts 101 is a curved clamp bar 166 about the center of which is disposed a pressure pad 102 adjustably shiftable toward or away from the head carrying arm of the sewing machine by means of the adjusting bolt 103.

Understanding now the portion of the apparatus for clamping and severing the needle thread of the sewing machine, now consider that part of the apparatus which is operative to sever the bobbin thread of the sewing machine. This portion of the apparatus is illustrated in combination with the sewing machine in FIGURE 2 and is separately illustrated in the showings of FIG- As also best 7 tion of the mechanism. As

URES 6, 8 and 14 through 18. As best seen in the showing of FIGURE 2 the sewing machine is provided with a cylindrical stud 1114 secured to and extending downward from the bed plate upon which is mounted the unit 1115 which conjointly with the structure of the throat plate34 comprise the bobbin thread cutting porbest seen in FIGURES 6 and 8, the unit 165 includes a mounting block 1% vertically bored as at 107 so that the unit may he slipped onto the stud 104 and fixedly secured in position thereto by means of the locking screw 1138. Disposed upon opposite sides of the mounting block 1% and extending toward the bobbin 36 are a pair of side plates designated respectively as 1119 and 1113, the side plate 109 being secured to the mounting block 1% as by means of the screws 111 and the side plate being similarly secured to the mounting block 1% by means of the screws 112.

Fixedly secured to the lower edge of side plate 1119 is an insulating terminal board 113 which carries two sets of electrical contact plug prongs designated respectively as114 and 115. Also mounted to the side plate 16? is the rotary solenoid 116 effective to clockwise rotate the upper end of lever 117 about pivot 118 through the intervening links 119 and 1211, as best seen in FIGURES 2, 6 and 14. Such rotation of lever 117 occurs when the rotary solenoid 116 is actuated by energization via its conductor leads 121 which are electrically connected to plug prongs 114. As best seen in FIGURES 8, 14 and 15, an insulator block 122 is secured to side plate 1159 as by means of the machine screws 123, the insulator block carrying a pair of contact sleeves 124 electrically energizable via electrical conductors 125 the opposite ends of which connect to plug prongs 115 mounted upon terminal'board 113.

Secured to the underside of the throat plate 34 as by means of screws 126 is an insulator terminal block 12'? carrying a pair of plug prongs 128 seatable downward into the contact sleeves 124 carried by the side plate 111%. The prongs 128 have extending therefrom electrical conductors 129 which feed respectively into a pair of ceramic insulating sleeves 130 and close through a resistance wire element 131. The ceramic sleeves 131) are cemented into recesses cut upward from the underside of the throat plate 34- so as to position the resistance wire element 131 immediately adjacent to the needle hole 132 with the sleeves 131B lying between the normally existing feed dog slots as for example illustrated at 133. Directly underlying the insulating sleeves 1319 is a slider element 134 disposed within a milled slot 135 extending transversely of the throat plate 34 and within which the slider 134 is disposed for reciprocating motion, the screws 136 serving to retain the slider 134 in proper position. The slider is slotted as at 137 to permit the normal sewing machine feed dogs to pass upward therethrough and is provided at one end with a socket hole 138 within which the upper end of lever 117 is adapted for disposition to shift the slider 134 and cause the land 13? between the slider feed dog slots'137 to shift the bobbin thread over against the resistance Wire element 131 carried by the insulating sleeves 131) and to thereby sever the bobbin thread when the resistance wire element is in a heated state.

Electrical energization of the rotary solenoid 116 and the resistance wire element 131 from terminal board 113 may be effected simultaneously or sequentially as desired, and may be simultaneous with the energization of the presser foot resistance wire element 49 and actuation of needle thread clamp 56, or again may be carried out in a desired sequence. Operation of the thread cutting system according to the invention may be effected manually, as for example by operator actuation of a switch, or may be carried out automatically in combination with operation of an automatic needle positioning mechanism which causes the sewing machine needle to rise to its upper position and then actuate the trimming apparatus.

Having now described my invention in connection with a particularly illustrated embodiment thereof, it will be appreciated that modifications and variations of my invention may now occur from time to time to those persons normally skilled in the art without departing from the essential scope or spirit of the invention, and accordingly it is intended to claim the same broadly as well as specifically as indicated by the appended claims.

What is claimed as new and useful is:

1. A thread trimming device for severing the needle thread of a sewing machine which includes a reciprocating needle having an eye therein through which said thread extends, comprising in combination, an electrically energizable heat generating element, sewing machine presser foot means for supporting said element in operative position in closely spaced relationship to the upper surface of an article being stitched, means for coupling said element to a source of electrical energization, means for clamping the needle thread at a point along its length between the needle eye and the said heat generating element including actuatable means carried by said presser foot for shifting the needle thread first into clamped engagement with a clamping element and then into engagement with said electrically energizable heat generating element, whereby the needle thread may be severed at a point between the article being stitched and the point at which it is clamped.

2. in combination with a sewing machine which includes a reciprocating needle having an eye therein through which a needle thread extends, a thread trimming device for severing said needle thread comprising an electrically energizable heat generating element, sewing machine presser foot means for supporting said element in operative position in closely spaced relationship to the upper surface of an article being stitched, means for coupling said element to a source of electrical energization, means carried by said presser foot for clamping the needle thread at a point along its length between the needle eye and the said heat generating element including actuatable means for shifting the needle thread first into clamped engagement with a clamping element and then into engagement with said electrically energizable heat generating element, and means carried by the sewing ma chine eflective to reduce the needle thread tension when the needle thread is being shifted by said actuatable means, whereby the needle thread may be severed at a point between the article being stitched and the point at which it is clamped.

3. A thread trimming device for severing the needle thread of a sewing machine, comprising in combination, a sewing machine presser foot carrying an electrically energizable heat generating resistance wire in laterally spaced close proximity to the axis of reciprocation of the sewing machine needle, said resistance wire being physically fixed to said presser foot and electrically insulated therefrom by means having the ability to withstand without breakdown the maximum temperature developed in said resistance wire, means for coupling said resistance wire to a source of electrical energization, and selectively actuatable means carried by said presser foot for laterally shifting the needle thread into engagement with the said electrically energizable heat generating resistance wire.

4-. A thread trimming device for severing the needle thread of :a sewing machine which includes a reciprocating needle having an eye therein through which said thread extends and means for tensioning said thread, comprising in combination, a sewing machine presser foot having a toe portion carrying an electrically energizable heat generating resistance wire in laterally spaced close proximity to the axis of reciprocation of the sewing machine needle, said resistance wire being physically fixed to said presser foot and electrically isulated therefrom by means having the ability to withstand without breakdown the maximum temperature developed in said resistance wire, means for coupling said resistance wire to a source of electrical energization, and selectively actuatable means carried by said presser foot for clamping the needle thread at a point along its length between the needle eye and the said resistance wire and laterally shifting the needle thread into engagement with the said electrically energizable heat generating resistance wire.

5. The thread trimming device as set forth in claim 4 wherein said presser foot carried needle thread clamping and shifting means includes a fixed clamp member overlying at least a portion of a toe of said presser foot, and a movable clamp part shiftable transversely through the axis of reciprocation of the sewing machine needle effective to catch the needle thread and clamp the same against the said member.

6. The thread trimming device as set forth in claim d wherein said presser foot carried needle thread clamping and shifting means includes a fixed clamp member overlying at least a part of said toe portion of said presser foot, and a movable clamp part shiftable transversely through the axis of reciprocation of the sewing machine needle etfective to catch the needle thread and clamp the same against the said member, and further including, thread tension reducing means operable during movement of said movable clamp part effective to reduce the needle thread tension by disabling the sewing machine needle thread tensioning means when the needle thread is being shifted by said movable clamp part.

7. The thread trimming device as set forth in claim 4 wherein said presser foot carried needle thread clamping and shifting means includes a fixed clamp member overlying :at least a portion of a toe of said presser foot, and a movable clamp part shiftable transversely through the axis of reciprocation of the sewing machine needle effective to catch the needle thread and clamp the same against the said member, and further including, thread tension reducing means operable during movement of said movable clamp part effective to reduce the needle thread tension by disabling the sewing machine needle thread tensioning device when the needle thread is being shifted by said movable clamp part, and actuating means coupled both to said selectively actuatable means carried by said presser foot and to said thread tension reducing means to synchronously actuate the same.

8. The thread trimming device as set forth in claim 4 wherein said presser foot carried needle thread clamping and shifting means includes a fixed clamp member overlying at least a portion of a toe of said presser foot, and a movable clamp part shiftable transversely through the axis of reciprocation of the sewing machine needle eifective to catch the needle thread and clamp the same against the said member, and further including, thread tension reducing means operable during movement of said movable clamp part effective to reduce the needle thread tension by disabling the sewing machine needle thread tensioning device when the needle thread is being shifted by said movable clamp part, and actuating means coupled both to said selectively actuatable means carried by said presser foot and to said thread tension reducing means to synchronously actuate the same, said actuating means including adjustable means for altering within limits the synchronous actuation of said tension reducing means and presser foot carried selectively actuatable means.

9. The thread trimming device as set forth in claim 4 wherein the thread severing portion of said resistance wire overlies a portion of a toe of said presser foot and is more remote from the axis of needle reciprocation than is the inside edge of the presser foot toe, said presser foot carried needle thread clamping and shifting means includes a fixed clamp member non-engagingly overlying said resistance wire and a movable clamp part shiftable transversely through the axis of reciprocation of the needle effective to catch the needle thread and clamp the same against the fixed clamp member and then move the thread against the thread severing portion of said resistance wire.

10. A thread trimming device for severing the needle thread of a sewing machine which includes a reciprocating needle, comprising in combination, a sewing machine presser foot carrying an electrically energizable heat generating resistance wire in laterally spaced close proximity to the axis of reciprocation of the sewing machine needle, said resistance wire being physically fixed to said presser foot and electrically insulated therefrom by means having the ability to withstand without breakdown the maximum temperature developed in said resistance wire, means for coupling said resistance wire to a source of electrical energization, selectively actuat-able means carried by said presser foot for laterally shifting the needle thread into engagement with the said electrically energizable heat generating resistance wire, and means operable to reduce the needle thread tension when the needle thread is being shifted by said actuatable means.

11. A thread trimming device for severing the bobbin thread of a sewing machine having a throat plate provided with a needle hole therethrough, comprising in combination, an electrically energizable heat generating resistance wire carried by the sewing machine throat plate in closely spaced underlying relationship to the under surface of an article being stitched with the thread severing portion of the resistance wire disposed immediately adjacent to the needle hole in the throat plate, thread shifting means carried by said throat plate effective when actuated for shifting the bobbin thread into positive engagement with said resistance wire, electrically energizable actuating means for selectively actuating said thread shifting means, and means for coupling said resistance wire and actuating means to a source of electrical energization.

12. A thread trimming device for severing the bobbin thread of a sewing machine having a threat plate provided with a needle hole therethrough, comprising in combination, an electrically energizable heat generating element, means for supporting said element in closely spaced underlying relationship to the undersurface of an article being stitched, a shiftable member carried by the throat plate in position between the bobbin and the throat plate needle hole and disposed so that the bobbin thread passes therethrough, electrically energizable actuating means coupled to said shiftable member and efiective when energized to shift said member to thereby shift the bobbin thread into positive engagement with said heat generating element, and means for coupling said heat generating elementand said actuating means to a source of electrical energlzation.

13. A thread trimming device for severing the bobbin thread of a sewing machine having a throat plate provided with a needle hole and feed dog slots therethrough, comprising in combination, an electrically energizable heat generating resistance wire carried by the sewing machine throat plate in closely spaced underlying relationship to the under surface of an article being stitched with the thread severing portion of the resistance wire disposed immediately adjacent to the needle hole in the throat plate, thread shifting means carried by said throat plate in underlying relation to said resistance wire and disposed so that the bobbin thread passes therethrough effective when actuated for shifting the bobbin thread into positive engagement with said resistance wire, electrically energizable actuating means detachably coupled to said thread shifting means for selectively actuating said thread shifting means, and means for coupling said. resistance wire and actuating means to a source of electrical energization.

14. The thread trimming device according to claim 13 wherein said thread shifting means is a slider element slidably disposed immediately beneath the throat plate enemas one end detachably drivingly engaged with said slider.

16. A thread trimming device for severing one of the needle and bobbing threads of a sewing machine, comprising in combination, an electrically energizable heat generating element, support means for supporting said element in closely spaced relationship to one surface of an article being stitched and to the thread to be severed, means for coupling said element to a source of electrical energization, and means carried directly by said support means for shifting the thread into engagement with said electrically energizable heat generating element to there by sever the thread when said element is energized.

17. A thread trimming device for severing one of the needle and bobbing threads of a sewing machine, comprising in combination, an electrically energizable heat generating element, support means for supporting said element, said element support means being adapted to be pressed against the article being stitched to position the element supported thereby in closely spaced relationship to one surface of an article being stitched and to the thread to be severed, means for coupling said element to a source of electrical energization, and means carried directly by said support means for shifting the thread into engagement with said electrically energizable heat generating element to thereby sever the thread when said element is energized.

10. A thread trimming device for severing the needle and bobbin threads of a sewing machine, comprising in combination, a first electrically energizable heat generating element and first support means for supporting the same in closely spaced relationship to the upper surface of an article being stitched and to the needle thread to be severed, means carried by said first support means for shifting the needle thread into engagement with said electrically energizable heat generating element to thereby sever the needle thread when said element is energized, a second electrically energizable heat generating element and second support means for supporting the same in closely spaced relationship to the undersurface of the article being stitched and to the bobbin thread to be severed, means carried by said second support means for shifting the bobbin thread into engagement with said electrically energizable heat generating element to thereby sever the bobbin thread When said element is energized, and means for coupling said first and second electrically energizable heat generating elements to a source of electrical energization.

References Cited by the Examiner UNITED STATES PATENTS 2,064,881 12/36 Bowman 112254 2,398,473 4/46 Stahl et al. 112252 X 2,707,927 5/55 Artzt 112-252 2,908,237 10/59 Winberg 112-260 2,914,010 11/59 Cohen 112-252 3,050,970 8/62 Billi 66-145 X FOP EIGN PATENTS 310,510 1/ 19 Germany.

311,048 2/19 Germany.

JORDAN FRANKLIN, Primary Examiner.

DAVID J. WTLLIAMOWSKY, Examiner. 

1. A THREAD TRIMMING DEVICE FOR SEVERING THE NEEDLE THREAD OF A SEWING MACHINE WHICH INCLUDES A RECIPROCATING NEEDLE HAVING AN EYE THEREIN THROUGH WHICH SAID THREAD EXTENDS, COMPRISING IN COMBINATION, AN ELECTRICALLY ENERGIZABLE HEAT GENERATING ELEMENT, SEWING MACHINE PRESSER FOOT MEANS FOR SUPPORTING SAID ELEMENT IN OPERATIVE POSITION IN CLOSELY SPACED RELATIONSHIP TO THE UPPER SURFACE OF AN ARTICLE BEING STITCHED, MEANS FOR COUPLING SAID ELEMENT TO A SOURCE OF ELECTRICAL ENERGIZATION, MEANS FOR CLAMPING THE NEEDLE THREAD AT A POINT ALONG ITS LENGTH BETWEEN THE NEEDLE EYE AND THE SAID HEAT GENERATING ELEMENT INCLUDING ACTUATABLE MEANS CARRIED BY SAID PRESSER FOOT FOR SHIFTING THE NEEDLE THREAD FIRST INTO CLAMPED ENGAGEMENT WITH A CLAMPING ELEMENT AND THEN INTO ENGAGEMENT WITH SAID ELECTRICALLY ENERGIZABLE HEAT GENERATING ELEMENT, WHEREBY THE NEEDLE THREAD MAY BE SEVERED AT A POINT BETWEEN THE ARTICLE BEING STITCHED AND THE POINT AT WHICH IT IS CLAMPED. 